Release: add commit changelog generator script

Add a bash script to generate markdown changelog between two git
references (tags/commits) with automatic GitHub PR association.

Features:
- Extracts commit info using git log with custom format
- Links commits to GitHub PRs via GitHub API
- Supports custom repository specification

The script requires GITHUB_TOKEN environment variable and jq for
JSON parsing. Outputs markdown format suitable for release notes.

You can see a demo case in our 2.0.0 changelog:
- https://cloudberry.apache.org/releases/2.0.0-incubating

Author: tuhaihe

devops/release/generate-changelog.sh

@@ -0,0 +1,101 @@
+#!/usr/bin/env bash
+# ======================================================================
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# ======================================================================
+#
+# Generate changelog between two git references (tags/commits)
+# Usage: ./generate-changelog.sh <from_ref> <to_ref> [repo_owner/repo_name]
+#
+# Examples:
+#   ./generate-changelog.sh 1a40e1f 8178d4f
+#   ./generate-changelog.sh v1.0.0 v1.1.0
+#   ./generate-changelog.sh 1a40e1f 8178d4f apache/cloudberry
+#   ./generate-changelog.sh v1.0.0 v1.1.0 apache/cloudberry
+#
+# GitHub Token Setup:
+# 1. Go to GitHub Settings > Developer settings > Personal access tokens > Tokens (classic)
+# 2. Generate new token with 'repo' scope (for private repos) or 'public_repo' scope (for public repos)
+# 3. Export the token: export GITHUB_TOKEN=your_token_here
+
+set -e
+
+# Default values
+DEFAULT_REPO="apache/cloudberry"
+GITHUB_API_BASE="https://api.github.com"
+
+# Function to display usage
+usage() {
+    echo "Usage: $0 <from_ref> <to_ref> [repo_owner/repo_name]"
+    echo ""
+    echo "Examples:"
+    echo "  $0 1a40e1f 8178d4f"
+    echo "  $0 v1.0.0 v1.1.0"
+    echo "  $0 1a40e1f 8178d4f apache/cloudberry"
+    echo "  $0 v1.0.0 v1.1.0 apache/cloudberry"
+    echo ""
+    echo "Environment variables:"
+    echo "  GITHUB_TOKEN - GitHub personal access token (required)"
+    exit 1
+}
+
+# Check arguments
+if [ $# -lt 2 ] || [ $# -gt 3 ]; then
+    usage
+fi
+
+FROM_REF="$1"
+TO_REF="$2"
+REPO="${3:-$DEFAULT_REPO}"
+
+# Check if GITHUB_TOKEN is set
+if [ -z "$GITHUB_TOKEN" ]; then
+    echo "Error: GITHUB_TOKEN environment variable is required"
+    echo "Please set it with: export GITHUB_TOKEN=your_token_here"
+    exit 1
+fi
+
+# Check if jq is installed
+if ! command -v jq &> /dev/null; then
+    echo "Error: jq is required but not installed"
+    echo "Please install jq using your system's package manager"
+    exit 1
+fi
+
+# Count total commits first
+total_commits=$(git log --oneline "$FROM_REF..$TO_REF" | wc -l | tr -d ' ')
+
+echo "Generating changelog for $REPO from $FROM_REF to $TO_REF..."
+echo "Found $total_commits commits to process"
+echo ""
+
+# Generate changelog
+git log --oneline --pretty=format:"%h|%H|%s|%an" "$FROM_REF..$TO_REF" | while IFS='|' read -r short_sha full_sha subject author; do
+    # Get PR number for this commit
+    pr_number=$(curl -s -H "Authorization: token $GITHUB_TOKEN" \
+        "$GITHUB_API_BASE/repos/$REPO/commits/$full_sha/pulls" | \
+        jq -r '.[0].number // empty')
+
+    if [ -n "$pr_number" ]; then
+        echo "* [\`$short_sha\`](https://github.com/$REPO/commit/$full_sha) - $subject ($author) [#$pr_number](https://github.com/$REPO/pull/$pr_number)"
+    else
+        echo "* [\`$short_sha\`](https://github.com/$REPO/commit/$full_sha) - $subject ($author)"
+    fi
+done
+
+echo ""
+echo "Changelog generation completed!"